Apparatuses for connecting pipes, which are also called pipe couplings, are known in a wide variety of designs. Particularly favored are pipe couplings with which two pipe ends can easily be connected and released from one another again without any additional tools. Depending on the area of application for the pipelines, various demands are made of the pipe couplings to be used.
Efficient pipe couplings should make it possible to turn or pivot the connected pipes relative to one another, even in the laid state, without any negative impact upon the flow through or the function of the coupling. In addition, it should also be possible to use pipe couplings in lines to which high pressures are applied.
Pipe couplings are also used in lines in which two pipes run substantially coaxially into one another. These lines are known as a double pipe or also as a double jacketed pipe.
A generic pipe coupling for double jacketed pipes is known from DE 10 2009 052 674 A1. The pipe coupling shown makes provision for the connection of two pipelines lying one inside the other. There is a high pressure line on the inside here which is designed for pressures of up to approximately 400 bar, whereas the outer pipe is used as a return line (with pressures of approximately 40 to 70 bar). In order to be able to produce such a connection in conjunction with the necessary pipes a sliding sleeve (“telescopic pipe”) is provided which after the welding of the inner pipe establishes the connection between the outermost pipe and the pipe coupling part.
This type of structure has numerous disadvantages, in particular from the aspect of production. The sliding sleeve constitutes an additional component which is required in order to be able to produce the different weld connections and in order to equalize length tolerances of the pipes. As a result of this five weld connections are required in order to produce a pipe with the corresponding pipe coupling parts. Between the sliding sleeve and the outer pipe located on the inside there is, moreover, the risk of increased onset of corrosion because an appropriate protective layer (galvanization for example) can not be applied in this area. Moreover, the pipe coupling parts made in one part have very large dimensions, and this is why solid material often has to be chosen as a source material for the machining because thick-walled pipes are not available in this size range. In addition to the high production complexity for processing this solid material, high costs also occur.